Gene-Editing Advance May Allow Pig Organ Transplants to Humans

Scientists on Thursday announced a breakthrough in producing the first batch of live pigs free of risky viruses, setting the stage for transplanting life-saving organs from the animals into humans. Between 2012 and 2016, there was a almost 20 percent increase in the number of transplants that happened in the United States, and that number is only expected to increase as the population grows older, according to the United Network for Organ Sharing. This could theoretically make "xenotransplantation" (i.e., the transfer of organs from animals to humans) a safe option, especially considering the complementary biology that certain pig organs have with their homo sapien counterparts.

But that soon could become an issue of the past.

There is a drastic shortage of organs available for transplants around the world. "The real breakthrough will be when people are moving around for years with pig organs, only then will we really know that it's safe and effective". Researchers refer to them as porcine endogenous retroviruses - PERVs for short. Emerging technologies, like the CRISPR-Cas9 system of gene editing fame, are getting researchers closer to rejection free transplants. However, pigs also have many viruses embedded in their DNA, passed down the generations in sperm and eggs.

Creating PERV-free pigs is the first step in a four-step process to ultimately create pig organs suitable for human transplant or "xenotransplantation", Dr. Luhan Yang, a co-founder of eGenesis and the company's chief science officer, explained to HuffPost. What's more, retroviruses replicate by inserting a copy of their genome into their host's so those viruses may have been part of the pig genome for the roughly 25 million years that pig species have existed.

Those virus-free cells were then used to fertilize several pig embryos, which were implanted in sows who have since given birth to virus-free pigs.

Robin Weiss of University College London, who first discovered PERVs, says there are other viruses in the pig genome that could theoretically jump across to people, so although the risk of cancer or other problems has been reduced, it has not been completely eliminated.

Scientists have been introducing human cells into animals to create models of diseases for decades, yet the 2009 policy suspended funding for chimera-based research due to ethical concerns. He and his colleagues recently attempted to chop PERV genes out of pig cells with an editing technology called zinc finger nucleases, but the many imprecise DNA cuts proved toxic to cells. In 1984, "Baby Fae" famously received a heart transplant from a baboon and died 20 days later. So far, the animals have lived more than a year with no problems, Tector said. And, he said, the pigs would be anesthetized and killed humanely.

From those cells you can clone pigs that grow up, at which point you can take the organs from them.